JP3939025B2 - Method of assembling stainless hot-rolled steel sheets for building structures with excellent corrosion resistance - Google Patents

Description

【００２５】
本願発明のＮｏ．１〜４，６ではさび発生は殆ど認められず、かつ、溶着金属、ボンド、熱影響部ともに良好な靱性を示している。
【００２６】
【発明の効果】
本発明によれば、戸建て住宅、集合住宅、大型建築物、ビルディングや橋梁等の建造物の構造部材として耐食性に優れる鋼材を安価に供給するとともに、耐食性および靱性の優れた溶接部を有する組立方法を提供することを可能としたものである。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method for assembling steel materials used as structural members of buildings such as detached houses, apartment houses, large buildings, buildings and bridges.
[0002]
[Prior art]
Due to stricter building safety standards and the pursuit of functionality, steel materials for pillars and beams are required to have higher functionality. In particular, corrosion resistance is an important factor that affects the service life of a structure. Improvement of its properties is required, and stainless steel for building structures that has been free from rust has attracted attention.
[0003]
For structural use, SUS304 (18Cr-8Ni), which has excellent corrosion resistance and toughness, has many uses. However, since stainless steel such as SUS304 contains Ni in addition to Cr, the material cost is also high, and the number of times of annealing including solution treatment is high, and a high annealing temperature is required, so the manufacturing cost is also high, Although it was excellent, there was a problem in economic efficiency. Thus, although rust and corrosion are inevitable, steel materials are being developed that are inexpensive, suppress the progress of corrosion, and minimize the amount of corrosion.
[0004]
For example, in Japanese Patent Application Laid-Open No. 60-162507, the surface scale of a slab of ordinary steel is removed, glass paper is attached and rough-rolled, and then the molten film of the formed glass is removed and finish rolling is performed. A method for producing a black skin scale film having excellent adhesion and corrosion resistance is disclosed.
[0005]
Japanese Patent Application Laid-Open No. 8-199289 discloses a steel containing 0.50 to 1.50% Cr, and an oxide scale having a thickness of 10 μm or less having a chromium oxide film between the base material and the scale in a hot rolling process. An H-section steel having is disclosed.
[0006]
[Problems to be solved by the invention]
However, Japanese Patent Application Laid-Open No. 60-162507 has a problem that workability and safety are increased due to work at high temperatures during the hot rolling process, and the number of processes increases with the attachment and peeling of glass paper, and Decrease in production capacity is unavoidable and production costs increase, so that corrosion resistance is improved, but problems remain in economic efficiency.
[0007]
Japanese Patent Laid-Open No. 8-199289 is a technique for forming an oxide layer having excellent corrosion resistance on the surface of ordinary steel that has been inferior in corrosion resistance. Therefore, when corrosion progresses through the oxide layer, the effect of improving corrosion resistance is lost, so it is impossible to maintain a low corrosion rate below that of ordinary steel over a long period of time in a humid environment. It is impossible to improve the long-term durability of buildings.
[0008]
By the way, when considering a structural material such as a pillar or beam of a building, the corrosive environment is roughly divided into the period of use after that until the exterior material is completed. In the latter case, free inflow of outside air is not so severe as a corrosive environment as compared with the exterior material. Rather, although the time is short, the corrosiveness of the environment is more severe in the former period where it is directly exposed to wind and rain or dust. Therefore, if the amount of corrosion in a short period of time until the construction of the building is completed is the main amount of corrosion of the building structural material, and the steel has corrosion resistance that can withstand the environment, an expensive stainless steel such as SUS304 is used. It can be used without using steel.
[0009]
In view of the present situation, the present invention has studied a stainless steel hot-rolled steel sheet as an inexpensive building structural material that retains corrosion resistance with Cr, and an object of the present invention is to provide a welding method that is excellent in corrosion resistance and toughness during assembly. It is said.
[0010]
[Means for Solving the Problems]
The present invention solves the problem of maintaining corrosion resistance at the time of construction for a building structure, and the gist thereof is as follows.
(1) In mass %,
C: 0.005 to 0.022 %, Si: 0.05 to 1.5%,
Mn: 0.05 to 1.5%, P: 0.04% or less,
S: 0.05% or less, Cr: 10-15%,
N: 0.055 % or less, and
C + N: Corrosion resistance characterized by welding a stainless hot-rolled steel sheet satisfying 0.077 % or less and the balance being Fe and inevitable impurities so that the average Cr content of the deposited metal is 10% or more by weight%. An excellent method for assembling stainless steel hot-rolled steel sheets for building structures.
[0011]
(2) Stainless steel hot-rolled steel sheet is further mass %,
Mo: 0.1-2.5%, Cu: 0.1-2.5%,
Ni: 0.1 to 2.5%
One or more of these are contained, The assembly method of the stainless steel hot rolled steel sheet for building structures as described in said (1) characterized by the above-mentioned.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Next, the reason for limiting the range of each component in the present invention will be described.
First, the reasons for limiting the components of the stainless hot-rolled steel sheet will be described.
C is an effective element for improving the strength of steel. However, if it is less than 0.005%, the strength required for structural steel cannot be obtained. Moreover, the excessive addition exceeding 0.022 % reduces remarkably the base material toughness and the toughness of the heat affected zone. For this reason, the C content is set to 0.005 to 0.022 %.
[0013]
Since Si needs to be added to molten steel in order to reduce dissolved oxygen in the steel and ensure hot workability as a deoxidizer, it was set to 0.05% or more. On the other hand, if added over 1.5%, the toughness of the base metal and the welded portion is impaired, so the Si content was set to 0.05 to 1.5%.
[0014]
Mn needs to be added to molten steel as a deoxidizer and desulfurizer. If it is less than 0.05%, a predetermined effect cannot be obtained. On the other hand, if added over 1.5%, the toughness and cracking properties of the base metal and the welded portion are impaired, so the Mn content was set to 0.05 to 1.5%.
[0015]
When P is present in a large amount, not only the weldability is impaired, but also a phenomenon that promotes the generation of rust appears. Therefore, the content of P is set to 0.04% or less.
[0016]
S is not only a starting point for rust as a sulfur-based inclusion such as MnS, but also increases the corrosion rate. Furthermore, it segregates at the grain boundaries and harms hot workability. Therefore, it is necessary to regulate to 0.05% or less. S is more preferable as an impurity.
[0017]
Cr has the effect of suppressing the occurrence of corrosion and reducing the corrosion rate in the atmospheric environment. Also, once corrosion occurs and a rust layer is formed, it has the effect of reducing the overall corrosion rate of the steel material under the rust layer. However, if the amount of Cr added is less than 10%, the effect of weakening rust generation and reducing the corrosion rate is weak. On the other hand, in steel added with Cr exceeding 15%, the raw material cost and the manufacturing cost are increased, so the economic efficiency is lowered. From the above, the content of Cr is set to 10 to 15%.
[0018]
Mo, like Cr, has the effect of suppressing the occurrence of corrosion and reducing the corrosion rate in the atmospheric environment. Accordingly, when the effect of improving the corrosion resistance by adding Cr is weak, Mo is added as necessary. However, if the amount is small, the effect is weak, and if it is added excessively, raw material costs and manufacturing costs increase, and the economic efficiency decreases. Therefore, when adding Mo, 0.1 to 2.5% is included.
[0019]
Cu and Ni have the effect of suppressing the occurrence of corrosion and reducing the corrosion rate in the atmospheric environment, like Cr. Also, since it is an austenite-generating element, it promotes the precipitation of grain boundary martensite in the weld heat-affected zone, and suppresses coarsening of crystal grains and also suppresses a decrease in toughness. . However, if the amount is small, the effect is weak, and if it is added excessively, raw material costs and manufacturing costs increase, and the economic efficiency decreases. Then, when adding Cu and Ni, 0.1 to 2.5% is contained.
[0020]
N is an element that improves the strength of the steel, but excessive addition significantly reduces the toughness of the base metal and the weld heat affected zone. Therefore, the N content is 0.055% or less. Furthermore, since C has the same effect as N, C + N is set to 0.077 % or less.
[0021]
Second, the reasons for limiting the components of the weld metal in the present invention will be described.
Cr has the effect of suppressing the occurrence of corrosion and reducing the corrosion rate in the atmospheric environment of the weld metal, but if the Cr content is less than 10%, the effect is weak with respect to the suppression of rust generation and the reduction of the corrosion rate. Therefore, the average content of the weld metal is limited to 10% or more. In order to obtain such a weld metal, for example, welding may be performed using a stainless steel welding material containing a predetermined amount of Cr.
[0022]
【Example】
Hereinafter, the present invention will be described in detail based on examples.
The prototype steel shown in Table 1 was melted in a converter and cast into a slab by continuous casting. Then, after reheating to 1100 degreeC-1300 degreeC temperature range with a heating furnace, it rolled to thickness 3mm with the rough rolling mill and the finish rolling mill. Using these steels as a base material, a groove of 60 ° was produced with the oxide scale attached. Welding is performed under the conditions of 140 to 250 A-20 to 26 V-10 to 80 cm / min using 5 types of welding wires containing 5%, 9%, 13%, 18%, and 22% by mass of Cr. MIG welding was performed, and the average Cr amount of the deposited metal is also shown in Table 1. Note that preheating and post heat treatment are not performed during welding.
[0023]
Regarding the rust resistance of the deposited metal, a 5% NaCl aqueous solution heated to 35 ° C. was sprayed for 100 hours, and the occurrence of red rust was observed with the naked eye. Moreover, about the toughness of a weld metal, a bond, and a HAZ part, the 2.5 mm subsize test piece was produced and the Charpy test was implemented. In the rust resistance test results shown in Table 1, ○ indicates that no rust is generated, × indicates that rust is generated, and in the impact test results, ○ indicates a fracture surface transition temperature of −30 ° C. or lower, and × indicates a fracture surface. The transition temperature exceeds -30 ° C.
[0024]
[Table 1]

[0025]
No. of the present invention. In 1 to 4 and 6 , almost no rust was observed, and the weld metal, bond, and heat-affected zone showed good toughness.
[0026]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to the present invention, an assembling method having a welded portion having excellent corrosion resistance and toughness as well as supplying steel material having excellent corrosion resistance as a structural member of a building such as a detached house, an apartment house, a large building, a building or a bridge. It is possible to provide.

Claims (2)

% By mass
C: 0.005% to 0.022 %,
Si: 0.05 to 1.5%,
Mn: 0.05 to 1.5%
P: 0.04% or less,
S: 0.05% or less,
Cr: 10 to 15%,
N: 0.055 % or less, and
C + N: Corrosion resistance characterized by welding a stainless hot-rolled steel sheet satisfying 0.077 % or less and the balance being Fe and inevitable impurities so that the average Cr content of the deposited metal is 10% or more by weight%. An excellent method for assembling stainless steel hot-rolled steel sheets for building structures. Stainless hot-rolled steel sheet, with further mass%,
Mo: 0.1 to 2.5%,
Cu: 0.1 to 2.5%,
Ni: 0.1 to 2.5%
One or more of these are contained, The welding method of the stainless hot-rolled steel plate for building structures of Claim 1 characterized by the above-mentioned.